Columns are differential mass transfer apparatus in which the dispersion of immiscible liquids occurs during mechanical mixing (rotary disc column, RDC) or by passing through perforated plates under applied pulsation (pulsed column, PC).
Columns can be used to work with liquids containing insoluble residue.
The centrifugal extractor is a mass transfer apparatus in which the emulsion is disengaging in the field of the centrifugal forces. This reduces the internal volume of the apparatus and increases performance.
Centrifugal extractors are used to work with persistant emulsions or expensive substances.