Salt permeability constant

An exact mathematical relationship is obtained between the salt rejection and total volume flux in reverse osmosis based on a purely phenomenological theory assuming constant salt permeability. This approach does not require a specific membrane model ... 

Examination of equation 12 shows that water separation rate increases with the Water Permeability Constant K. Unfortunately, the salt flux across the membrane also does, resulting in a more salty product. An approximation for this salt flow is... 

Table 3 Results from the history matches cases A-G and M and N using diffusion and Darcy flow of methane gas balances, diffusion constants and rock salt permeabilities ...

A is often referred to as the water permeability constant. Note that if the soluble spedes rejection is not complete, the osmotic pressure difference across the membrane must be related to the osmotic pressure difference between the feed and the permeate streams, instead of that between the feed and pure water. Another factor commonly reported for membrane performance is the salt or solute rejection efficiency (ratio), R, defined as... 

The evaluation of the apparent ionization constants (i) can indicate in partition experiments the extent to which a charged form of the drug partitions into the octanol or liposome bilayer domains, (ii) can indicate in solubility measurements, the presence of aggregates in saturated solutions and whether the aggregates are ionized or neutral and the extent to which salts of dmgs form, and (iii) can indicate in permeability measurements, whether the aqueous boundary layer adjacent to the membrane barrier, Umits the transport of drugs across artificial phospholipid membranes [parallel artificial membrane permeation assay (PAMPA)] or across monolayers of cultured cells [Caco-2, Madin-Darby canine kidney (MDCK), etc.]. 

With a three-component system, such as a polymer in an aqueous salt solution, preferential adsorption of one component to the polymer can affect the analysis of light-scattering data.199 Such interactions can affect the SRI. Therefore, measurements of the SRI must be made at constant chemical potential. Constant chemical potential is achieved experimentally by dialyzing the solvent and polymer solution to equilibrium through a membrane permeable to the solvent but impermeable to the polymer.199... 

Because of the high water permeability of the proximal tubule, water is reabsorbed in direct proportion to salt reabsorption in this segment. Thus, luminal fluid osmolality and sodium concentration remain nearly constant along the length of the proximal tubule (Figure 15-2). An experimental impermeant solute like inulin will rise in concentration as water is reabsorbed (Figure 15-2). If large amounts of an impermeant solute such as mannitol are present in the tubular fluid,... 

An electrochemical system, important particularly in biological systems, is one in which the species are ions and the system is separated into two parts by a rigid membrane that is permeable to some but not all of the species. We are interested in the conditions attained at equilibrium, the Donnan equilibrium. Two cases, one in which the membrane is not permeable to the solvent (nonosmotic equilibrium) and the other in which the membrane is permeable to the solvent (osmotic equilibrium), are considered. The system is at constant temperature and, for the purposes of discussion, we take sodium chloride, some salt NaR, and water as the components. The membrane is assumed to be permeable to the sodium and chloride ions, but not to the R-ions. We designate the quantities pertinent to the solution on one side of the membrane by primes and those pertinent to the solution on the other side by double primes. 

It is assumed that the best catalytic effect can be achieved if the pA a or pA), value of the interphase material is close to 7 [71]. Some weak ion-exchange groups such as tertiary amines, phosphoric acid, carboxylic acids, or pyridine show the required dissociation constant or p ta-values. Certain heavy metal ion complexes, such as chromium(lll)- or iron(Ill)-complexes, provide the required catalytic water dissociation effect. In principle, there are many more suitable metal ions available. The metal ions or complexes are immobilized by either including an insoluble salt in the casting solution of the interface layer between the ion permeable layers or by converting a soluble form by a follow-up treatment [45]. An additional requirement for the catalytic material is to be effective and stable for a long period. It must also remain in the interphase, where it is the most active, for the anticipated lifetime of the membrane. 

Red cell deformation takes place under two important constraints fixed surface area and fixed volume. The constraint of fixed volume arises from the impermeability of the membrane to cations. Even though the membrane is highly permeable to water, the inability of salts to cross the membrane prevents significant water loss because of the requirement for colloidal osmotic equilibrium [Lew and Bookchin, 1986). The constraint of fixed surface area arises from the large resistance of bilayer membranes to changes in area per molecule [Needham and Nunn, 1990]. These two constraints place strict limits on the kinds of deformations that the cell can undergo and the size of the aperture that the cell can negotiate. Thus, a major determinant of red cell deformability is its ratio of surface area to volume. One measure of this parameter is the sphericity, defined as the dimensionless ratio of the two-thirds power of the cell volume to the cell area times a constant that makes its maximum value 1.0 ... 

All these measures are applicable to monitor the development of the properties of the rock during loading and deformation. The development of the dilatancy can be divided very roughly into three phases. Phase I characterizes a decrease of the volume attributed to elastic compression of the rock salt, a decrease of permeability and an increase of seismic velocity. The volume becomes nearly constant at the end of Phase I. It can be assumed that elastic compression processes and dilatancy processes balance at this point. Dilatant microcracking generates only weak AE activity. 

In the absence of reliable viscometric data, the apparent viscosity values (evaluated using Darcy s law with the permeability of water) show a discontinuity around aqueous to oil ratio of 2 1. For several salt concentrations and phase ratios, the apparent viscosity variation with emulsion flow rate is essentially constant. 

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