nanofiltteröintiä

Nanofiltteröinti (nanofiltration) is a membrane separation process that removes larger dissolved molecules and suspended solids from a liquid. It operates at pressures typically between 5 and 30 bar, falling between reverse osmosis and ultrafiltration in terms of pore size and operating pressure. Nanofiltration membranes have pore sizes ranging from approximately 0.001 to 0.01 micrometers.

The primary function of nanofiltration is to selectively reject multivalent ions, such as divalent cations (e.g., calcium and magnesium) and anions (e.g., sulfate), while allowing monovalent ions (e.g., sodium and chloride) to pass through to some extent. This selective rejection makes it particularly useful for water softening, removing hardness-causing ions. It can also effectively remove organic molecules with molecular weights above approximately 200-400 g/mol, as well as color, dissolved organic matter (DOM), and certain pesticides.

Common applications of nanofiltration include municipal water treatment for softening and nitrate removal, as well as industrial processes such as dairy processing for demineralization and whey protein concentration, pharmaceutical production for solvent recovery and purification, and textile wastewater treatment for dye removal. The process is energy-efficient compared to processes like reverse osmosis when high salt rejection is not the primary goal. The lifespan of nanofiltration membranes can be affected by factors such as feed water quality, operating conditions, and proper cleaning protocols.