permeatflux

Permeatflux is a term used in membrane science to describe the rate at which a permeant crosses a barrier per unit area under a driving force. It is often considered a specialized form of permeate flux, with emphasis on the transport of specific solutes or solvents through a membrane or selective barrier. In practice, permeatflux is expressed in units such as mol m^-2 s^-1 or L m^-2 h^-1, representing the amount of permeant passing through the membrane per unit area per unit time.

Definition and context can vary, but permeatflux generally refers to the net transport of a permeant from the feed side to the permeate side. Under steady conditions, it is influenced by both the properties of the membrane (thickness, porosity, pore size distribution, hydrophobicity or hydrophilicity, surface charge) and the driving force (pressure difference, concentration gradient, or electrochemical potential). Temperature and fouling also modify the observed flux by altering diffusivity and resistance at the membrane surface.

Measurement methods typically involve controlled laboratory setups such as diffusion cells or crossflow filtration rigs. The permeate side is monitored for concentration or volume over time, and flux is calculated as J = V_p/(A t) or J = (dN)/(A dt). Accurate assessment may require accounting for concentration polarization, membrane compaction, and fouling.

Applications of permeatflux concepts appear in water treatment and desalination, food and beverage filtration, pharmaceutical purification, and bioprocessing. The term is closely related to, and sometimes used interchangeably with, permeate flux, though some sources distinguish it for specific experimental or contextual uses.