Membrane separation is a process that uses a semi-permeable membrane to separate substances based on their size, charge, or chemical properties. This technique is commonly used in various industries, including water treatment, food processing, and pharmaceuticals, to purify or concentrate specific components from mixtures. The membranes can be made from different materials, such as polymers or ceramics, and can operate under various conditions, including pressure and temperature. Membrane separation methods include ultrafiltration, nanofiltration, and reverse osmosis, each suited for specific applications and separation requirements.