dc.description.abstract | In this study, a facile fabrication of superhydrophobic Cu mesh for oil-water separation is applied in a low-temperature vacuum environment. When the predominant composition of surface is CuO, it’s a hydrophilic substrate with contact angle 56o, and oil cannot be separated from water due to the penetration of both oil and water. After this facile fabrication, the composition of surface changes into Cu2O partially, and it becomes a superhydrophobic substrate with contact angle 152.6o. Oil-water separation can be achieved because oil penetrates the superhydrophobic mesh while water is repelled on the mesh. And the separation efficiency can be higher than 99%. In addition, there’s no chemicals coated on mesh in this fabrication, so the stability is pretty high. The mesh can be against various aqueous chemical drops such as salts, acid, base, and surfactant. Besides, if the pore size of a mesh is shrunk and a mesh remains hydrophobicity, the stability can be elevated and operated in an environment of higher intrusion pressure.
Nanofiltration membranes sometimes are used as the material for oil-water separation. Due to the small pore size (1-10 nm), the operation pressure should be higher than atmospheric pressure. In order to improve the performance in future works, the wetting behavior of nanofiltration membrane (Dow FILMTEC™ NF270) is investigated in this study. The contact angle of NF270 produced by Dow Chemical is 20.8o which is hydrophilic, and also it has ultralow contact angle hysteresis. A small bubble (1.6 μL) can slide steadily on 2o-inclined NF270. Because of the ultralow contact angle hysteresis, a bubble doesn’t deform and move on the surface with spherical shape. Without the effect of shape, it becomes easier to observe bubble motion in surfactant solution. Besides, nanofiltration membranes are also used to reject specific salt ions for water softening. Generally, there’s positive or negative function group on a nanofiltration membrane to reject co-ions. However, besides the effects of function group and ion size, the ions in a solution also compete and the permeation ions varies. For NaCl solution, Cl- permeates NF270 more, while for CH3COONa solution, Na+ permeates NF270 more. By measuring the potential difference and comparing the correlation of various solutions, the ion permeation can be understood easily and straightforward. | en_US |