MEMBRANES Types

MEMBRANES are a viable means of water treatment, petroleum refining, sterilization,dairy processing etc. Implementation of membranes in these fields has progressed using more advanced membranes made from new materials and employed in various configurations.

               Membranes are largely differenciated on the basis of the FILTRATION TECHNIQUES used. There are FOUR most commonly used types of FILTRATION TECHNIQUES –

I]  MICRO-FILTRATION :

               Microfiltration is a type of physical filtration process where a contaminated fluid is passed through a special pore-sized membrane to separate microorganisms and suspended particles from process liquid. It usually serves as a pre-treatment for other separation processes such as ultrafiltration, and a post treatment for granular media filtration.

II] ULTRA-FILTRATION :

Ultrafiltration is a separation process using membranes with pore sizes in the range of 0.1 to 0.001 micron. UF membranes are characterized by their molecular weight cut-off. Typically, UF membranes will remove high molecular-weight substances, colloidal materials, color, odour and organic and inorganic polymeric molecules. Low molecular-weight organics and ions such as sodium, calcium, magnesium chloride, and sulfate are not removed by UF Membranes.

III] REVERSE OSMOSIS :

           

 Reverse osmosis is a water purification technology that uses a semipermeable membrane. This membrane technology is not properly a filtration method. In RO, an applied pressure is used to overcome osmotic pressure, a colligative property, that is driven by chemical potential. RO can remove many types of molecules and ions from solutions and is used in both industrial processes and in producing potable water.

IV] NANO-FILTRATION :

               Nano-filtration is a pressure related process, during which separation takes place, based on molecule size where membranes bring about the separation. Nano-filtration functions similarly to reverse osmosis, but is generally targeted to remove only divalent and larger ions. Monovalent ions such as sodium and chloride will pass through a nanofiltration membrane, therefore many of its uses involve de-salting of the process stream.