- The Nano filtration process is a Reverse Osmosis process using a relatively open RO membrane, allowing water and small univalent ions (Na+, K+, Cl-) to pass. The filtration process takes place on a selective separation layer formed by an organic semi permeable membrane. The driving force of the separation process is the pressure difference between the feed (retentiate) and the filtrate (permeate) side at the separation layer of the membrane. However, because of its selectivity, one or several components of a dissolved mixture are retained by the membrane despite the driving force, while water and substances with a molecular weight < 200 D are able to permeate the semi permeable separation layer.
- Nano filtration membrane also has selectivity for the charge of the dissolved components, monovalent ions will pass the membrane and divalent and multivalent ions will be rejected. The nano filtration technique is mainly used for the removal of two valued ions and the larger mono valued ions such as heavy metals.