Semipenneable membrane

Bartkow, M.E. Huckins, J.N. Muller, J.F. 2004, Field-based evaluation of semipenneable membrane devices (SPMDs) as passive air samplers of polyaromatic hydrocarbons (PAHs). Atmos. Emiron. 38 5983-5900. 

In physics, an elastic two-dimensional plate is tenned a membrane (Latin membram = parchment) but in chemistry the tenn denotes a body, usually thin, which serves as a phase separating two other bulk phases. If this body is penneable to the same degree for all components of the adjacent phases and does not affect their mobility, then its only function is to prevent rapid mixing of the two phases. This is then tenned a diaphragm. A real membrane must exhibit a certain selectivity, based on different penneability for the components of the two phases, and is then tenned a semipenneable membrane. Membranes separating two electrolytes that are not penneable to the same degree for all ions are called electrochemical membranes. It is with these that we are concerned here. 

Electrodialysis is the combined process of dialysis electrolysis using semipenneable membranes to confine the soln under treatment... 

If we represent the magnitude of this applied hydrostatic pressure by n, then the chemical potential of water on the right-hand side of the semipenneable membrane in Figure 2-8 is +RT In aw +Fwn. This solution is in equilibrium with pure water on the left-hand side of the membrane, where = /i,. Hence, + RT In aw + Vwn =, or RT In aw +VWII = 0,... 

Parrott, J.L., S.M. Backus, A.I. Borgmann and M. Swyripa. The use of semipenneable membrane devices to concentrate chemicals in oil refinery effluent on the Mackenzie River. Arctic 52 125—138, 1999. 

The complexation of complementary polyelectrolytes can be exploited for the formation of skins of various shapes. For instance, Larez et al. [155] reported the formation of spherical assemblies (diameters up to 500 pm) by letting drops of a chitosan solution free fall into a solution of oxidized scleroglucan (Fig. 31). The skin of the assembly, separating the external polyanion from the internal polycation solution, acted as a semipenneable membrane. The possibility of encapsulating a micelle within the primary spherical skin was suggested as a model for the organization of cells containing a nucleus where a variety of reactions could be performed with a release of products in the external solution. 

Osmosis is a natural process involving fluid flow across a semipenneable membrane barrier. The phenomenon of osmosis occurs when pure water flows from a dilute saline solution through a membrane into a higher concentration saline solution. Its chemical potential, which is a function of pressure, temperature, and concentration of dissolved solids, determines the direction of solvent flow. This process can be reversed by applying pressure to the concentrate solution, causing water to flow from the concentrated solution into the dilute solution (Fig. 13.4). These membranes permit the passage of water molecules but are a barrier to most of the dissolved solids in water. 

PURPOSE AND RATIONALE The ultrafiltration (UF) with semipenneable, size-exclusion membranes produces a separation of the free drug from macromolecules by employing a pressure... 

---