Nanoscale Pore Size Research Articles

Regeneration of supercritical carbon dioxide by membrane at near critical conditions

The separation of supercritical carbon dioxide from a mixture of carbon dioxide and caffeine with a membrane possessing nano-scale pore size was studied. The experimental data indicated that a 100% caffeine rejection could be obtained at the condition of 308 K and approximately 7.95 MPa which is near the critical point of carbon dioxide. Besides the caffeine rejection the highest carbon dioxide permeation flux also occurred at the same operating condition. The highest caffeine rejection and carbon dioxide permeation flux were caused by the presence of a large cluster size in the near critical region. Under this situation, caffeine clusters could not be allowed to enter into pores of the membrane. When the temperature and pressure are increased, both the caffeine rejection and carbon dioxide permeation flux would be reduced due to a reduction of cluster sizes.

膜の構造制御と機能 相転換法による膜構造制御

The control of 3-dimensions membrane structure is of primary concern in the development of new separation membranes. Here, a new possibility for separation membrane is presented using a phase inversion process. The structure of the asymmetric membrane fabricated by a dry/wet phase inversion process showed an ultrathin skin layer and sponge-like structure characterized by the presence of macrovoids. We have prepared a series of asymmetric membranes with different defect-free skin layer thicknesses from 10 to 5.0×103nm by the dry/wet phase inversion.The gas selectivity of the asymmetric membrane increases with a decrease in the surface skin layer thickness, which may be due to the fact that the surface skin layer of the membrane with a thinner thickness forms a more packed structure. On the other hand, porous membranes with nanoscale pore sizes are of interest in areas such as catalysis, sensors, size-and shape-selective separation media, adsorbents, and scaffolds for composite materials synthesis.Those with pore sizes on the order of 1nm to 10μm are required. A new possibility for porous membrane is presented using a phase inversion process.