Nanofiltração

Nanofiltração is a membrane filtration process that falls between reverse osmosis and ultrafiltration in terms of pore size. Its membranes typically have pore sizes ranging from 0.001 to 0.01 micrometers. This allows nanofiltration to effectively remove divalent ions, larger monovalent ions, and uncharged organic molecules while allowing smaller monovalent ions and water to pass through.

The primary applications of nanofiltration include water softening, the removal of color and dissolved organic matter from surface water, and the concentration of valuable components in industrial processes. In water treatment, it is particularly useful for reducing hardness by removing calcium and magnesium ions. It can also be employed to remove pesticides, herbicides, and other organic contaminants. In the food and beverage industry, nanofiltration is used for demineralization, sugar concentration, and the clarification of juices.

Nanofiltration membranes are typically made from polymers such as polyamides or polysulfones. The process operates at moderate pressures, usually between 5 and 20 bar, depending on the feed water characteristics and the specific membrane used. The selectivity of nanofiltration membranes can be influenced by factors such as membrane material, charge, and operating conditions. While it offers a good balance between separation efficiency and energy consumption, membrane fouling can be a challenge that requires appropriate pre-treatment and cleaning strategies.