Media migration

As long ago as 1809 Reuss observed that clay particles, dispersed In aqueous media, migrate under the influence of an applied electric fleld. This was an early example of electrophoresis, the most familiar electrokinetlc phenomenon. 

Migration is greater from polypropylene than from high-density polyethylene. Little migration is found to aqueous media. Migration is highest into n-heptane, ethanol and com oil. 

Separation principle Migration in a single separation medium Migration in different separation media Migration and interaction with the sorbent Migration, interaction with the sorbent, diffusion and detection reaction... 

Voltammetry in Weakly Supported Media Migration and Other Effects... 

Molecular Weight Class Viscosity at 25 °C (cP) Efficiency Low-Temperature Properties Hydrocarbons Resistance to Aqueous media Migration... 

Most nonfixed-pore structure filters are subject to media migration. This means that parts of the filter medium become detached and continue to pass downstream, contaminating the effluent (fluid that has passed through the filter). Media migration is also sometimes incorrectly taken to include release of "built-in" contamination—for example, dust and fibers picked up by the filter during its manufacture. 

Nonfixed-pore structure filters do not have absolute ratings, are subject to media migration, and unload particles very badly on impulse. A comparison of dirt capacity between fixed-pore and nonfixed-pore depth filters is meaningless because the nominal removal ratings of nonfixed-pore structure filters bear little relationship to their behavior in service. 

Granular media filters fall in the category of nonfixed-pore filters because the filter media are not held rigidly in place. Thus, if not backwashed promptly, granular media filters can unload previously filtered solids. Media migration, however, is usually not a problem because media screens are usually built into the filter vessel, preventing the media from leaving the filter vessel. 

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