Nano filtration is a technique that has succeeded in the course of recent years which is used most often with low total dissolved solids water such as surface water and fresh groundwater. Divalent and larger ions are generally targeted to be removed by Nano filtration. Monovalent ions pass through Nano filtration membrane so it is widely used for desalting application. Removing hardness and dissolved organics from water, arsenic removal from drinking water, heavy metal ions recovery from electroplating waste water and separation of pharmaceuticals from fermentation broths are some of the examples of industrial applications of nano filtration. NF has properties that lie between Ultra filtration (UF) and Reverse Osmosis (RO) with pore size of 0.01-0.001 µm. Since all NF membranes have their origins in reverse osmosis (RO) membranes, they are called loose reverse osmosis membranes or tight ultra filtration membranes with respect to its permeate flux and separation performance.
Pervaporation is a process in which a specific component in a liquid feed mixture passes through a dense, non-porous membrane by solution – diffusion transport mechanism. Permeate is collected as vapour on one side while the other side of the membrane is kept under vacuum conditions. Some of the Applications include Dehydration of Organic Solvents. The PV process can easily dehydrate solvent mixtures. The binary or ternary azeotropes can be dehydrated without the use of entrainers. In some cases, where distillation is not possible, pervaporation is the only alternative to costly incineration of waste solvent streams.