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Sectioning of membrane unit: Partitioning of technological scheme into sections in each certain hydrodynamic and mass transfer regimes are realized.
Selective layer (selective membrane skin): Region, often located at the upstream face of an asymmetric membrane, that forms a thin, distinguishable layer primarily responsible for determining the permeability of the asymmetric membrane.
Selective membrane: Membrane capable to selective permeation of certain components of a mixture.
Selectivity of membranes: Capability of membranes for selective permeation of certain components of feed mixture.
Separation coefficient, SC(AB): Ratio of the compositions of component A and В in the downstream relative to the ratio of compositions of these components in the upstream {Note 1: For example, if compositions are expressed in mole fractions (ХA and XB), SC(AB) = [XA/XB]downstream / [XA/XB]upstream}(Note 2: The separation coefficient can also be defined equivalently in terms of concentrations in the downstream and upstream, since only ratios are involved) [Note 3: The separation coefficient refers to a local relationship between concentrations on the upstream and downstream concentrations while the separation factor refers to retentate and permeate leaving the module].
Separation factor, SF(AB): Ratio of the compositions of components A and В in the permeate relative to the composition ratio of these components in the retentate. [Note 1: For example, SF(AB) = [XA/XB]Permeate/[XA/XB]Retentate} (Note 2: The separation factor can also be defined in terms of concentrations in the permeate and retentate since only ratios are involved.)
Size distribution of pores: Size dependence of the number or fraction of pores.
Sol-gel membrane formation: Multistep process for making membranes by a reaction between two chemically multifunctional materials dissolved in a solvent that results in a network structure with solvent retained in the network followed by heat treatment to achieve a desired pore structure.
Solution - diffusion (sorption - diffusion) mechanism: Molecular-scale process in which penetrant is sorbed into the upstream membrane face from the external phase, moves by molecular diffusion in the membrane to the downstream face and leaves into the external gas, vapor or liquid phase in contact with the membrane.
Stage cut: Parameter defined as the fractional amount of the total feed entering a membrane module that passes through the membrane as permeate.
Stage of membrane process: A part of technological scheme of multi-stage process of membrane separation.
Support of composite membrane: A layer that provides robustness of composite membrane.
Surface porosity: The fraction of surface area of membrane free of its material.
Surface potential of membranes: Electrical potential that appears at the surface of membranes due to dissociation of its functional groups.
Sweep (purge) gas: Nonpermeating stream directed past the downstream membrane face to reduce downstream permeant concentration.
Swelling of membranes: Increases in membrane volume due to its sorption of compounds from liquid or gas (vapor) phase.
Synthetic (artificial) membrane: Membrane formed by a process not occurring in nature.
