Membranseparation

Membranseparation, commonly referred to as membrane separation, is a class of physical separation processes that use a semi-permeable membrane to allow certain species to pass while retaining others. Separation is driven by a pressure, concentration, or electrical potential gradient, and selectivity arises from differences in size, solubility, or interactions with the membrane material.

Common membrane processes include microfiltration, ultrafiltration, nanofiltration, and reverse osmosis, arranged by increasing solute retention. Microfiltration removes suspended solids and some colloids; ultrafiltration targets macromolecules and colloids; nanofiltration excludes small ions and organic molecules; reverse osmosis achieves high salt rejection and is used for desalination. Other approaches include gas separation membranes, pervaporation, and electrodialysis.

Typical membrane modules are hollow fiber, spiral-wound, and plate-and-frame designs. Materials are mainly polymeric, with growing use of inorganic and mixed-matrix membranes to improve stability and selectivity.

Applications span drinking water treatment, wastewater reclamation, seawater desalination, food and beverage processing, pharmaceutical purification, and gas purification such as carbon dioxide removal. In bioprocessing, membranes are used for clarification and product recovery.

Advantages include energy-efficient separations and modular scalability; challenges include membrane fouling, concentration polarization, and chemical or thermal instability. Ongoing research focuses on fouling resistance, higher permeate flux, and lower costs through new materials and configurations.