Nanofiltration is a membrane filtration process that operates between ultrafiltration and reverse osmosis. It uses membranes with pore sizes typically ranging from 1 to 10 nanometers, allowing it to selectively remove small particles, organic molecules, and divalent ions while letting monovalent ions pass through. This makes it effective for water treatment and softening. The technology is commonly used in various applications, including water purification, food processing, and wastewater treatment. Nanofiltration can improve the quality of drinking water by reducing contaminants and is also employed in industries to concentrate or separate specific substances from mixtures.