We used molecular dynamics simulation to demonstrate the microscopic wetting behavior of two solid model surfaces for the first time.Hydrophilic and hydrophobic features were modeled in a dense CO2 fluid environment under various densities.The water droplet loses contact with the surface under the influence of higher density CO2 fluids on the hydrophobic surface.For the hydrophilic surface,no separation between the water droplet and the surface was observed.However,the contact angle of the water droplet on the hydrophilic surface was found to increase with the fluid density.The effect of dense CO2 fluid on the surface wettability can be interpreted in terms of enhanced interactions from the surrounding CO2 molecules.
Extraction of heavy metal ions from solid matrix by means of an incorporation of chelating agents with supercritical carbon dioxide(scCO2) was investigated experimentally. Four commercially available chelating agents, diethylammonium diethyldithiocarbamate(Et2NH2DDC), trifluoroacetylacetone(TFA), hexafluoroacetylacetone(HFA) and thenoyltrifluoroacetone(TTA) were tested. The extraction experiments were conducted at 50 °C and 1.39×107― 2.80×107 Pa. According to the experimental results, for the extraction of Cu2+, all the chelating agents investigated here are effective. For other metal ions, such as Pb2+, Ni2+ and Cd2+, Et2NH2DDC exhibited a better extraction result, while other chelating agents were less effective. This investigation is expected to provide a tentative evaluation on the scCO2-based metal extraction from solid media.
