Perstraction is the separation technique developed from liquid-liquid extraction. Due to the presence of the membrane a wider selection of extractants can be used, this can include the use of miscible solutions, for example the recovery of ammonia from waste water using sulphuric acid.
This process is analogous to pervaporation in some ways. But the permeate is in liquid phase. Perstraction technique eliminates the problem of phase dispersion and separation altogether.
A basic perstraction is called the single perstraction or membrane perstraction. An advantage is minimizing toxic damage to microorganisms or enzymes. Nevertheless, perstraction includes problems like expensive membranes, clogging and fouling of membranes.