Reverse Osmosis (RO) and Nanofiltration (NF) are advanced, pressure-driven membrane technologies crucial for water purification, desalination, and industrial separation. Both operate by applying pressure to overcome natural osmotic pressure, pushing water molecules through a semi-permeable membrane while rejecting impurities.

Uses dense, high-pressure membranes to reject almost all dissolved salts (monovalent/divalent), organic compounds, and microorganisms (>99% rejection). It is the standard for seawater/brackish water desalination.

An intermediate process between Ultrafiltration (UF) and RO, often called "membrane softening". It operates at lower pressures, allowing some monovalent ions (e.g., sodium, chloride) to pass while effectively removing multivalent ions (e.g., calcium, magnesium) and larger organic molecules. Key Performance Factors

Modern membranes utilize thin-film composite (TFC) structures, with emerging materials like graphene oxide (GO), carbon nanotubes (CNTs), and biomimetic materials showing promise for higher permeability and chemical resistance. Primary Applications

Fouling, or the accumulation of contaminants on the membrane surface, is the "Achilles' heel" of these systems, requiring robust pre-treatment (e.g., UF, chlorination, pH adjustment).