Introduction to Membrane Separation Technology

Definition of a Membrane

A membrane is a medium that performs molecular-level separation and filtration. When a solution or gas mixture comes into contact with a membrane, under pressure, an electric field, or a temperature difference, some substances can permeate through the membrane, while others are selectively intercepted. This separates different components in the solution or gas mixture; this separation is at the molecular level.

Types of Membranes

Separation membranes include: reverse osmosis membranes (0.0001–0.005 μm), nanofiltration membranes (0.001–0.005 μm), ultrafiltration membranes (0.001–0.1 μm), microfiltration membranes (0.1–1 μm), electrodialysis membranes, pervaporation membranes, liquid membranes, gas separation membranes, electrode membranes, etc. They correspond to different separation mechanisms, different equipment, and different applications. Membranes can be made of polymers, inorganic materials, or liquids, and their structures can be homogeneous or heterogeneous, porous or non-porous, solid or liquid, charged or neutral. Membrane thickness can range from as thin as 100 μm to as thick as a few millimeters. Different membranes have different microstructures and functions, requiring different preparation methods. Membrane fabrication methods have always been a core research topic in the membrane field and a closely guarded secret technology for various companies.

Definition of Membrane Separation Technology

By fabricating the above-mentioned membranes into configurations suitable for industrial use, and connecting them with driving equipment (pressure pumps, electric fields, heaters, or vacuum pumps), valves, instruments, and pipelines to form a device, and operating under certain process conditions, aqueous solutions or gas mixtures can be separated. The component that permeates through the membrane is called the permeate. This separation technology is called membrane separation technology.